1. Field of the Invention
The present invention relates to a denture provided with a layer of a soft relining material and to a method of repairing the denture. The invention further relates to a dental soft relining material used for such applications.
2. Description of the Prior Art
Patients who need a denture and, particularly, a full denture, in many cases, are aged persons, and their alveolar ridges must bear an increased occlusion force per a unit area since the bone has generally been resorbed to a conspicuous degree. The mucosa of alveolar ridge becomes thin due to senile atrophy, and the occlusion stress or masticatory pressure is not softened but is directly transmitted to the alveolar bone. Moreover, a thin mucosa disposed between a hard resin denture base and the hard alveolar bone is tightened and gets hurt after every occlusion, and begins to feel pain.
In such a serious case, the resin denture base molded by using a methyl methacrylate resin that is usually used is not sufficient for stably maintaining the mastication and supporting the adhesion of the denture. That is, it is necessary to reline the mucosa surface of the resin denture base with a soft dental relining material to compensate the lost viscoelasticity of the mucosa of the residual alveolar ridge, in order to impart cushioning property that softens the occlusal stress. That is, the object of relining with a soft material is to overcome various troubles that develop when the thin mucosa is compressed by the hard denture base.
Dental soft relining materials used, so far, for the clinic include a (meth)acrylic acid ester polymer, a fluorine-containing resin, a polyolefin type resin, a silicone rubber, and the like. For temporary applications, furthermore, there is used a denture adhesive.
However, the soft material such as the (meth)acrylic acid polymer or the like lacks chemical stability in the oral cavity, become hard and brittle within several months, and are not usable for extended periods of time. The fluorine type relining material lacks viscoelasticity from which sufficient cushioning effect cannot be expected. The polyolefin type relining material has many problems from a practical point of view. That is, it may deform the resin denture base because the preparation temperature is high, and it requires a plurality of adhesives and a special heating device, involving a cumbersome operation. The silicone rubber-type relining material is relatively stable but is not sufficient in regard to durability, especially straining, and operability, especially trimming. In particular, the soft relining materials that are now used in the clinic do not almost have machinability and cannot be corrected once they are cured.
Even as for the denture adhesive, the consistency increases as it is used for extended periods of time and the plasticity decreases. As a result, the fit and marginal shut of ill-fitting denture are not improved and, hence, the object of enhancing the stability and support of the denture base is not fully accomplished and, besides, the oral tissue is damaged in many cases. Moreover, since the denture has a small compressive stress and lacks elasticity, its cushioning effect is not sufficient for the occlusal stress and that becomes a cause of the recurrence of pain in the oral mucosa.
As described above, the dental soft relining material for denture base provided so far lost physical properties after the use of a short period of time, could be used in the oral cavity for only a short period of time, could not offer satisfactory cushioning effect, could be used requiring cumbersome method, and was not practicable. It has therefore been desired to provide a soft relining material for dental use having a suitable viscoelasticity, without losing physical properties, and having excellent operability and, particularly, machinability. In particular, the soft relining material for dental use having such properties is strongly demanded toward the coming aging society.